Reclining mechanism for vehicle seat

ABSTRACT

A reclining mechanism for a vehicle seat composed of a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat; a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a pair of diametrically opposed semi-circular ratchet portions concentric with the hinge pin; a pair of diametrically opposed slide pawls slidably coupled with the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portions of the second arm member; and a cam element slidably coupled with the first arm member in a lateral direction perpendicular to the slide pawls and disposed between the slide pawls, the cam element being operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawls with the ratchet portions of the second arm member and for disengaging the slide pawls from the ratchet portions of the second arm member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawls in engagement with the ratchet portions of the second arm member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reclining mechanism for a vehicle seat for adjusting an inclined angle of a back rest of the seat relative to a seat cushion.

2. Description of the Prior Art

Disclosed in Japanese Patent Laid-open Publication No. 8-52040 is a reclining mechanism for a vehicle seat which is composed of a pair of arm members for attachment to a frame structure of a seat cushion and to a frame structure of a back rest, the arm members being connected by means of a hinge pin for relative rotation about the hinge pin, a slide pawl slidably coupled with one of the arm members to be moved in a radial direction with respect to the hinge pin, and a cam element mounted on the hinge pin for rotation therewith and engaged with the slide pawl for maintaining the slide pawl in engagement with a ratchet portion of the other of the arm members and for disengaging the slide pawl from the ratchet portion when it is rotated with the hinge pin. In the reclining mechanism, the relative rotation of the arm members is restricted by engagement of the slide pawl with the ratchet portion to lock the back rest at an inclined angle and is permitted by disengagement of the slide pawl from the ratchet portion for adjustment of the inclined angle of the back rest.

In the reclining mechanism, the engagement of the slide pawl with the ratchet portion of the arm member is maintained in a condition where the slide pawl is pressed by engagement with a portion of the cam element. When the cam element is rotated with the hinge pin to disengage the slide pawl from the ratchet portion of the arm member, the slide pawl is retracted by engagement with a portion of the cam element. If the reclining mechanism is applied with a load, the slide pawl is slightly rotated due to an error in assembly of the component parts of the reclining mechanism. This results in looseness in engagement of the slide pawl with the ratchet portion of the arm member.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide a reclining mechanism for a vehicle seat wherein rotation of the slide pawl is prevented to firmly maintain the engagement of the slide pawl with the ratchet portion even if the reclining mechanism is applied with a load.

According to the present invention, the object is accomplished by providing a reclining mechanism for a vehicle seat, which comprises a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat, a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a semi-circular ratchet portion concentric with the hinge pin, a slide pawl slidably coupled with the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portion of the second arm member, and a cam element slidably coupled with the first arm member in a lateral direction perpendicular to the slide pawl and operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawl with the ratchet portion of the first arm member and for disengaging the slide pawl from the ratchet portion of the first arm member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawl in engagement with the ratchet portion of the second arm member, wherein the slide pawl is formed at its outer end with a semi-circular toothed portion to be engaged with the ratchet portion of the first arm member and its inner end with a pair of laterally spaced projections for engagement with a flat end surface of the cam element, and wherein the cam element is formed at the flat end surface thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawl for permitting disengagement of the slide pawl from the ratchet portion of the first arm member.

In a practical embodiment of the present invention, the first arm member is formed with a first guide groove in a radial direction with respect to the hinge pin and a second guide groove perpendicular to the first guide groove, and the slide pawl is slidably coupled within the first guide groove while the cam element is slidably coupled within the second guide groove. For operative connection of the cam element with the hinge pin, the cam element is formed with an elongated lateral hole in the lateral direction perpendicular to the slide pawl, and the hinge pin is inserted across the lateral hole of the cam element for connection to the first and second arm members and being engaged with a portion of the lateral hole of the cam element.

According to an aspect of the present invention, there is provided a reclining mechanism for a vehicle seat, which comprises a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat, a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a pair of diametrically opposed semi-circular ratchet portions concentric with the hinge pin, a pair of diametrically opposed slide pawls slidably coupled with the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portions of the second arm member, and a cam element slidably coupled with the first arm member in a lateral direction perpendicular to the slide pawls and disposed between the slide pawls, the cam element being operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawls with the ratchet portions of the second arm member and for disengaging the slide pawls from the ratchet portions of the second arm member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawls in engagement with the ratchet portions of the second arm member.

In a practical embodiment of the reclining mechanism described above, the slide pawls each are formed at their outer ends with a semi-circular toothed portion for engagement with each ratchet portion of the second arm members and at their inner ends with a pair of laterally spaced projections to be engaged with opposite flat surfaces of the cam element for maintaining the slide pawls in engagement with the ratchet portions of the second arm member, and wherein the cam element is formed with the opposite flat surfaces thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawls for permitting disengagement of the slide pawls from the ratchet portions of the second arm member.

In such an embodiment described above, it is preferable that a cam plate is assembled with the cam element to disengage the slide pawls from the ratchet portions of the second arm member by engagement therewith when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element. The cam plate is formed with a pair of diametrically opposed cam slots which are engaged with a pair of cam pins provided on the slide pawls to disengage the slide pawls from the ratchet portions of the second arm member when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element. In the embodiment, a movable cam plate may be assembled with the hinge pin to be rotated with the hinge pin and rotatably connected with the cam element to cause lateral movement of the cam element when rotated with the hinge pin, wherein the movable cam plate is formed with a pair of diametrically opposed cam slots which are engaged with a pair of cam pins provided on the slide pawls to disengage the slide pawls from the ratchet portions of the second arm member when the hinge pin is rotated against the load of the torsion spring.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will be more readily appreciated from the following detailed description of preferred embodiments thereof when taken together with the accompanying drawings, in which:

FIG. 1 is a partly broken front view of a reclining mechanism in accordance with the present invention;

FIG. 2 is a vertical sectional view of the reclining mechanism taken along line 2—2 in FIG. 1;

FIG. 3 is a cross-sectional view of the reclining mechanism taken along line 3—3 in FIG. 1;

FIG. 4 is a front view of a first arm member shown in FIG. 1;

FIG. 5 is a front view of a second arm member shown in FIG. 1;

FIGS. 6(a) to 6(c) illustrate a mode of operation of a cam element in the reclining mechanism shown in FIG. 1;

FIG. 7 is a vertical sectional view of a first modification of the reclining mechanism shown in FIGS. 1 to 3;

FIGS. 8(a) to 8(c) illustrate a mode of operation of a cam element in the first modification;

FIGS. 9(a) to 9(c) illustrate a mode of operation of a cam element in a second modification of the reclining mechanism shown in FIGS. 1 to 3;

FIG. 10(a) is a front view of the cam element shown in FIGS. 9(a) to 9(c);

FIG. 10(b) is a vertical sectional view of the cam element shown in FIG. 10(a);

FIG. 11(a) is a front view of a movable cam plate shown in FIGS. 9(a) to 9(c);

FIG. 11(b) is a vertical sectional view of the movable cam plate shown in FIG. 11(a);

FIGS. 12(a) and 12(b) illustrate a mode of operation of a cam element in a third modification of the reclining mechanism;

FIG. 13 is a vertical sectional view of the reclining mechanism taken along line 4—4 in FIG. 12(a);

FIG. 14 is a cross-sectional view of the reclining mechanism taken along line 5—5 in FIG. 12(a); and

FIG. 15 is a vertical sectional view of a modification of the reclining mechanism shown in FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrated in FIGS. 1 to 3 is a reclining mechanism for a vehicle seat in accordance with the present invention, which reclining mechanism is composed of a first arm member 11 for attachment to a frame structure of a seat cushion (not shown) of the vehicle seat, a second arm member 12 for attachment to a frame structure of a back rest (not shown) of the vehicle seat, a pair of slide pawls 13 and 14, a cam element 15, a torsion spring 16, a hinge pin 17 and an operation lever 18. The first and second arm members 11 and 12 are coupled to contain the slide pawls 13, 14 and cam element 15 therein. The second arm member 12 is connected to the first arm member 11 by means of the hinge pin 17 for relative rotation about the hinge pin 17. The reclining mechanism is assembled with the vehicle seat in such a manner that the second arm member 12 is locked to the first arm member 11 at a selected position to retain the back rest at an inclined angle and that the second arm member is released from the first arm member to permit adjustment of the inclined angle of the back rest.

As shown in FIGS. 1 to 4, the first arm member 11 has an upper portion 11 a formed to contain the slide pawls 13, 14 and cam element 15 and a lower portion 11 b for attachment to the frame structure of the seat cushion. As shown in FIG. 4, the upper portion 11 a of first arm member 11 is formed therein with a vertical guide groove 11 d across a central hole 11 c and a lateral guide groove 11 e perpendicular to the vertical groove 11 d. The vertical guide groove 11 d is slightly extended outward from the inner periphery of a circular recess 11 f formed in the upper portion 11 a, while the lateral groove 11 e is extended to the inner periphery of the circular recess 11 f.

As shown in FIGS. 1 to 3 and 5, the second arm member 12 has a lower portion 12 a formed to contain the slide pawls 13, 14 and cam element 15 and an upper portion 12 b for attachment to the frame structure of the back rest. The lower portion 12 a of second arm member 12 is formed with a circular recess 12 d concentric with a central hole 12 c. The circular recess 12 d and central hole 12 c are formed in the lower portion 12 a of second arm member 12 to correspond with the circular recess 11 f and central hole 11 c formed in the upper portion 11 a of first arm member 11. The circular recess 12 d of second arm member 12 is formed at its inner periphery with a pair of diametrically opposed semi-circular ratchet portions 12 e.

The slide pawls 13 and 14 are formed in the same width and thickness. As shown in FIG. 6, the slide pawls 13 and 14 are formed at their outer ends with semi-circular toothed portions 13 a and 14 a and at their inner ends with flat surfaces 13 b and 14 b and each pair of tapered projections 13 c and 14 c. The thickness of each of the slide pawls 13, 14 is determined to correspond with a space defined by the vertical guide groove 11 d of first arm member 11 and the circular recess 12 d of second arm member 12, and the width of each of the slide pawls 13, 14 is determined to correspond with the width of the vertical guide groove 11 d of first arm member 11. The semi-circular toothed portions 13 a, 14 a of slide pawls 13, 14 are positioned to be engaged with and disengaged from the ratchet portions 12 e of second arm member 12. The tapered projections 13 c, 14 c of slide pawls 13, 14 are formed to be located in the lateral guide groove 11 e of first arm member 11 in a condition where the slide pawls 13, 14 are maintained in engagement with the ratchet portions 12 e of second arm member 12.

As shown in FIGS. 6(a)-6(c), the cam element 15 is in the form of a rectangular plate which is formed at its central portion with an elongated lateral hole 15 a and at its opposite flat surfaces with each pair of laterally spaced recesses 15 b, 15 c. The lateral hole 15 a is formed at one side thereof with a radial recess 15 d. The thickness of the cam element 15 is determined to correspond with a space defined by the lateral guide groove 11 e of first arm member 11 and the circular recess 12 d of second arm member 12. The width of cam element 15 is determined to correspond with the width of lateral groove 11 e of first arm member 11, and the elongated lateral hole. 15 a of cam element 15 is formed to allow rotation and lateral movement of cam element 15 relative to the hinge pin 17. The laterally spaced recesses 15 b, 15 c of cam element 15 each are formed to be brought into engagement with and disengaged from the laterally spaced projections 13 c, 14 c of slide pawls 13, 14. The radial recess 15 d of cam element 15 is maintained in engagement with a radial projection 17 a of hinge pin 17.

During the assembly process of the reclining mechanism, the slide pawls 13, 14 are slidably engaged with the vertical guide groove 11 d of first arm member 11, and the cam element 15 is slidably engaged with the lateral guide groove 11 e of first arm member 11 and disposed between the slide pawls 13 and 14. Thereafter, the second arm member 12 is coupled at its lower portion 12 a with the upper portion 11 a of first arm member 11 for relative rotation and united with the first arm member 11 by engagement with upper and lower retainer plates 19 a and 19 b welded to the upper and lower portions 12 a and 11 a of second and first arm members 12 and 11. The retainer plate 19 a is slidably engaged at its lower end portion with a semi-circular upper end of first arm member 11, while the retainer plate 19 b is slidably engaged at its upper end portion with a semi-circular lower end of second arm member 12. When the second arm member 12 has been coupled at its lower portion 12 a with the upper portion 11 a of first arm member 11 as shown in FIGS. 1 and 2, the slide pawls 13, 14 and cam element 15 are contained in the circular recess 12 d of second arm member 12. In such a condition, the hinge pin 17 is inserted into the central hole 12 c of second arm member 12 across the central hole 11 c of first arm member 11 and the elongated lateral hole 15 a of cam element 15. In this instance, the radial projection 17 a of hinge pin 17 is engaged with the recess 15 d of cam element 15.

As shown in FIG. 3, a support plate 19 c is riveted to the upper portion 11 a of first arm member 11 and engaged with a stepped portion of hinge pin 17 to retain the hinge pin 17 in position. As shown in FIG. 1, the support plate 19 c is formed with a pair of hooks 19 d. The torsion spring 16 is engaged at its inner end with an outer end portion of hinge pin 17 and at its other end with one of the hooks 19 d to bias the hinge pin 17 in a counterclockwise direction so that the cam element 15 is retained at a central portion of lateral guide groove 11 e as shown in FIG. 6(a). The operation lever 18 is fixed to the outer end of hinge pin 17.

In a condition where the cam element 15 is retained at the central portion of lateral guide groove 11 e under the load of torsion spring 16 as shown in FIG. 6(a), the tapered projections 13 c, 14 c of slide pawls 13, 14 are maintained in engagement with the opposite flat surfaces of cam element 15 such that the slide pawls 13 and 14 are maintained in engagement with the semi-circular ratchet portions 12 e of second arm member 12 to restrict relative rotation of the second arm member 12 with respect to the first arm member 11. Thus, the back rest of the vehicle seat is retained at an inclined angle. When the operation level 18 is operated to rotate the hinge pin 17 against the load of torsion spring 16 in a clockwise direction, the cam element 15 is moved rightward as shown by an arrow in FIG. 6(a). The rightward movement of cam element 15 is restricted by abutment of the cam element 15 against the hinge pin 17 at the left-hand end of lateral hole 15 a. As a result, the tapered projections 13 c, 14 c of slide pawls 13, 14 are brought into engagement with the recesses 15 b, 15 c of cam element 15 to disengage the slide pawls 13, 14 from the ratchet portions 12 e of second arm member 12 as shown in FIG. 6(c). While the operation lever 18 is retained in its operated position, the slide pawls 13, 14 are retained in their disengaged positions from the ratchet portions 12 e of second arm member 12 to permit adjustment of the inclined angle of the back rest.

When the operation lever 18 is released after adjustment of the back rest, the hinge pin 17 is rotated under the load of torsion spring 16 in the counterclockwise direction to move the cam element 15 leftward as shown by an arrow in FIG. 6(c). During leftward movement of the cam element 15, the tapered projections 13 c, 14 c of slide pawls 13, 14 are disengaged from the recesses 15 b, 15 c of cam element 15 and brought into engagement with the opposite flat surfaces of cam element 15 to engage the slide pawls 13, 14 with the ratchet portions 12 e of second arm member 12 and to maintain the slide pawls 13, 14 in engagement with the ratchet portions 12 e of second arm member 12. In such a condition, each pair of spaced projections 13 c, 14 c of slide pawls 13, 14 engaged with the opposite flat surfaces of cam element 15 is useful to firmly maintain the slide pawls 13, 14 in engagement with the ratchet portions 12 e of second arm member 12 even if the reclining mechanism is applied with a load. As in the reclining mechanism, the hinge pin 17 is assembled across the elongated lateral hole 15 a of cam element 15 and engaged at its radial projection 17 a with the recess 15 d of the elongated lateral hole 15 a, the lateral movement of cam element 15 is smoothly effected by rotation of the hinge pin 17.

Illustrated in FIGS. 7 and 8(a)-8(c) is a first modification of the reclining mechanism shown in FIGS. 1 to 3. In this modification, a cam plate 21 is assembled with the cam element 15 to move the slide pawls 13, 14 toward and away from the ratchet portions 12 e of second arm member 12 in accordance with lateral movement of the cam element 15. As shown in FIG. 8(b), the cam plate 21 is in the form of a rectangular plate 21 a formed at its opposite sides with a pair of arm portions 21 b and formed with a pair of vertically spaced cam slots 21 c. The cam plate 21 is fixed to the cam element 15 at its both arm portions 21 b for movement therewith. The cam slots 21 c each are formed with an inclined portion and a horizontal portion. The slide pawls 13, 14 are provided thereon with cam pins 13 d, 14 d which are slidably engaged with the cam slots 21 c of cam plate 21.

In a condition where the spaced projections 13 c, 14 c of slide pawls 13, 14 are maintained in engagement with the opposite flat surfaces of cam element 15 as shown in FIG. 8(a), the slide pawls 13, 14 are maintained in engagement with the ratchet portions 12 e of second arm member 12, and the cam pins 13 d, 14 d are located in the horizontal portions of cam slots 21 c. When the operation level 18 is operated by the user to move the cam element 15 rightward as shown by an arrow in FIG. 8(a), the spaced projections 13 c, 14 c of slide pawls 13, 14 are brought into engagement with the recesses 15 b, 15 c of cam element 15, and the cam plate 21 is moved rightward with the cam element 15. As a result, the cam pins 13 d, 14 d are moved toward the cam element 15 by engagement with the inclined portions of cam slots 21 c to disengage the slide pawls 13, 14 from the ratchet portions 12 e of second arm member 12. When the operation lever 18 is released to move the cam element 15 leftward under the load of torsion spring 16 as shown by an arrow in FIG. 8(c), the spaced projections 13 c, 14 c of slide pawls 13, 14 are disengaged from the recesses 15 b, 15 c of cam element 15 and brought into engagement with the opposite flat surfaces of cam element 15 to engage the slide pawls 13, 14 with the ratchet portions 12 e of second arm member 12, while the cam plate 21 is moved leftward with the cam element 15, so that the cam pins 13 d, 14 d are located in the horizontal portions of cam slots 21 c.

Illustrated in FIGS. 9(a)-9(c) is a second modification of the reclining mechanism shown FIGS. 1 to 3. In this modification, a movable cam plate 22 is assembled with the cam element 15 to move the slide pawls 13, 14 toward and away from the the ratchet portions 12 e of second arm member 12 in accordance with lateral movement of the cam element 15. As shown in FIGS. 10(a) and 10(b), the cam element 15 is provided thereon with a pair of diametrically opposed support pins 15 e, 15 f for engagement with the cam plate 22. As shown in FIGS. 11(a) and 11(b), the cam plate 22 is formed at its central portion with a square hole 22 a and formed with a pair of diametrically opposed semi-circular cam slots 22 b and 22 c. The cam plate 22 is further formed with a circular hole 22 d for engagement with the support pin 15 e of cam element 15 and a semi-circular elongated hole 22 e which is slidably coupled with the support pin 15 f of cam element 15 to permit rotation of the cam plate 22 relative to the cam plate 15. The cam plate 22 is assembled with the hinge pin 17 at its square hole 22 a for rotation therewith and coupled with the support pins 15 e, 15 f of cam element 15 at its circular hole 22 d and semi-circular elongated hole 22 e. As shown in FIG. 9(b), the slide pawls 13, 14 are provided thereon with cam pins 13 d, 14 d which are slidably engaged with the cam slots 22 b, 22 c of cam plate 22.

In the reclining mechanism, the cam plate 22 is rotated with the hinge pin 17 to cause lateral movement of the cam element 15 in a direction perpendicular to the slide pawls 13 and 14. In a condition where the spaced projections 13 c, 14 c of slide pawls 13, 14 are maintained in engagement with the opposite flat surfaces of cam element 15 as shown in FIG. 9(a), the slide pawls 13, 14 a are maintained in engagement with the ratchet portions 12 e of second arm member 12, when the operation lever 18 is operated by the user against the load of torsion spring 16 to rotate the cam plate 22 in a clockwise direction, the cam element 15 is moved rightward by thrust force applied at its support pin 15 e from the cam plate 22 as shown by an arrow in FIG. 9(a), while the spaced projections 13 c, 14 c of slide pawls 13, 14 are brought into engagement with the recesses 15 b, 15 c of cam element 15. As a result, the cam pins 13 d, 14 d of slide pawls 13, 14 are moved toward the cam element 15 by engagement with the cam slots 22 b, 22 c of cam plate 22 to disengage the slide pawls 13, 14 from the ratchet portions 12 e of second arm member 12. When the operation lever 18 is released to rotate the hinge pin 17 under the load of torsion spring 36 in the counterclockwise direction, the cam plate 22 is rotated with the hinge pin 17 to move the cam element 15 leftward as shown an arrow in FIG. 9(c). As a result, the spaced projections 13 c, 14 c of slide pawls 13, 14 are disengaged from the recesses 15 b, 15 c of cam element 15 and brought into engagement with the opposite flat surfaces of cam element 15 to engage the slide pawls 13, 14 with the ratchet portions 12 e of second arm member 12.

Illustrated in FIGS. 12 (a)-12(b) and 14 is a third modification of the reclining mechanism shown in FIGS. 1 to 3, wherein the first arm member 11 is replaced with a first disk member 31 for attachment to the frame structure of the seat cushion and a second disk member 32 for attachment to the frame structure of the back rest. The first disk member 31 has a circular recess 31 a and vertical and lateral guide grooves 31 b, 31 c formed in the circular recess 31 a. The second disk member 32 has a circular recess 32 a formed at its inner periphery with a pair of diametrically opposed ratchet portions 32 b.

The second disk member 32 is coupled within the circular recess 31 a of first disk member 31 for relative rotation in such a manner that a radial projection 32 c of second disk member 32 is located in a semi-circular recess 31 d formed in the inner periphery of circular recess 31 a of first disk member 31. The radial projection 32 c of second disk member 32 is provided to restrict rotation of the second disk member 32 relative to the first disk member 31 by engagement with a stepped end of the semi-circular recess 31 d. As shown in FIG. 13, the first and second disk members 31 and 32 are united with each other by means of an annular bracket 39 a coupled therewith. The slide pawls 13, 14 and cam element 15 in the reclining mechanism shown in FIGS. 1 to 3 are replaced with slide pawls 33, 34 and cam element 35 which are contained in a space defined by the circular recesses 31 a and 32 a of disk members 31 and 32. The slide pawls 33, 34 are slidably coupled within the vertical guide groove 31 b of first disk member 31, while the cam element 35 is slidably coupled within the lateral guide groove 31 c and interposed between the slide pawls 33 and 34.

The slide pawl 33 is formed at its outer end with a semi-circular toothed portion and at its inner end with a pair of tapered projections 33 a and a recessed portion 33 b between the tapered projections 33 a. Similarly, the slide pawl 34 is formed at its outer end with a semi-circular toothed portion and at its inner end with a pair of tapered projections 34 a and a recessed portion 34 b between the tapered projections 34 a. The cam element 35 is formed at its opposite flat surfaces with each pair of laterally spaced recesses 35 a, 35 b and a pair of radially spaced projections 35 c, 35 d each of which is located between the recesses 35 a and between the recesses 35 b. In a condition where the slide pawls 33, 34 are engaged with the opposite flat surfaces of cam element 35 at their tapered projections 33 a, 34 a and maintained in engagement with the ratchet portions 32 b of second disk member 32 as shown in FIG. 12(a), the radial projections 35 c, 35 d of cam element 35 are disengaged from the recesses 33 b, 34 b of slide pawls 33, 34. When the cam element 35 is moved rightward, the radial projections 35 c, 35 d of cam element 35 are brought into engagement with the recesses 33 b, 34 b of slide pawls 33, 34 as shown in FIG. 12(b) to disengage the slide pawls 33, 34 from the ratchet portions 32 b of second disk member 32.

For connection with the cam element 35, the hinge pin 37 is integrally formed with a connecting arm 37 a which is located in an aperture 35 e formed in the cam element 35 and engaged with an inner periphery of the aperture 35 e. As shown in FIGS. 13, the hinge pin 37 is assembled with the disk members 31, 32 in such a manner as to permit rotation of the second disk member 32 relative to the first disk member 31 and loaded by a torsion spring 36 in a counterclockwise direction. When the hinge pin 37 is rotated by an operation lever (not shown) against the load of torsion spring 36 in a clockwise direction, the cam element 35 is moved rightward by engagement with the connecting arm 37 a of hinge pin 37. When the operation lever is released to rotate the hinge pin 37 in the counterclockwise direction under the load of torsion spring 36, the cam element 35 is moved leftward by engagement with the connecting arm 37 a of hinge pin 37. In FIG. 13, the reference numeral 39 b designates the frame structure of the seat cushion, and the reference number 39 c designates the structure of the back rest.

In a condition where the spaced projections 33 a, 34 a are maintained in engagement with the opposite flat surfaces of cam element 35, the slide pawls 33, 34 are maintained in engagement with the ratchet portions 32 b of second disk member 32 to retain the back rest at an adjusted angle. When the operation lever is operated to rotate the hinge pin 37 against the load of torsion spring 36 in the clockwise direction, the cam element 35 is moved rightward by engagement with connecting arm 37 a of hinge pin 37, while the spaced projections 33 a, 34 a of slide pawls 33, 34 are brought into engagement with spaced recesses 35 a, 35 b of cam element 35. During rightward movement of the cam element 35, the slide pawls 33, 34 are moved toward the cam element 35 by engagement with the projections 35 c, 35 d of cam element 35 at their recessed portions 33 b, 34 b and disengaged from the ratchet portions 32 b of second disk member 32. When the operation lever is released to rotate the hinge pin 37 in the counterclockwise direction under the load of torsion spring 36, the cam element 35 is moved leftward by engagement with the connecting arm 37 a of hinge pin 37, and the spaced projections 33 a, 34 a of slide pawls 33, 34 are disengaged from the recesses 35 a, 35 b of cam element 35 and brought into engagement with the opposite flat surfaces of cam element 35 to engage the slide pawls 33, 34 with the ratchet portions 32 b of second disk member 32.

As in the reclining mechanism, the radial projection 32 c of second disk member 32 is provided to restrict relative rotation of the second disk member 32 to the first disk member 31 by engagement therewith, the adjustment of the inclined angle of the back rest can be restricted in a predetermined extent in a simple construction.

Illustrated in FIG. 15 is a modification of the reclining mechanism shown in FIGS. 1 to 3. The modified reclining mechanism is composed of the same component parts as the disk members 31, 32, slide pawls 33, 34 and cam element 35 in the reclining mechanism shown in FIGS. 13 and 14. In this modification, the hinge pin 37 is in the form of a longitudinal connecting rod, and the connecting arm 37 a of cam element 37 is replaced with an arm portion 37 b 2 which is integrally formed with a sleeve 37 b 1 splined to the connecting rod 37 for rotation therewith. The arm portion 37 b 2 of sleeve 37 b 1 is engaged with the inner periphery of aperture 35 e of cam element 35 as shown in FIG. 12(a). The torsion spring 36 is disposed between the first disk member 31 and the arm portion 37 b 2 of sleeve 37 b 1 and assembled with the sleeve 37 b 1 to bias the connecting rod 37 in a counterclockwise direction. The connecting rod 37 can be adapted to operatively connect a pair of laterally spaced reclining mechanisms (not shown) mounted to opposite sides of a vehicle seat in a simple construction. 

What is claimed is:
 1. A reclining mechanism for a vehicle seat, comprising: a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat; a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a semi-circular ratchet portion concentric with the hinge pin; a slide pawl slidably coupled with the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portion of the second arm member; and a cam element slidably coupled with the first arm member in a lateral direction perpendicular to the slide pawl and operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawl with the ratchet portion of the first arm member and for disengaging the slide pawl from the ratchet portion of the first arm member; wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawl in engagement with the ratchet portion of the second arm member, wherein the slide pawl is formed at its outer end with a semi-circular toothed portion to be engaged with the ratchet portion of the first arm member and its inner end with a pair of laterally spaced projections for engagement with a flat end surface of the cam element, and wherein the cam element is formed at the flat end surface thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawl for permitting disengagement of the slide pawl from the ratchet portion of the first arm member.
 2. A reclining mechanism as claimed in claim 1, wherein the second arm member is coaxially coupled with the first arm member for relative rotation about the hinge pin.
 3. A reclining mechanism as claimed in claim 1, wherein the first arm member is formed with a first guide groove in a radial direction with respect to the hinge pin and a second guide groove perpendicular to the first guide groove, and wherein the slide pawl is slidably coupled within the first guide groove while the cam element is slidably coupled within the second guide groove.
 4. A reclining mechanism as claimed in claim 1, wherein the cam element is formed with an elongated lateral hole in the lateral direction perpendicular to the slide pawl, and wherein the hinge pin is inserted across the lateral hole of the cam element for connection to the first and second arm members and being engaged with a portion of the lateral hole of the cam element.
 5. A reclining mechanism for a vehicle seat, comprising: a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat; a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a pair of diametrically opposed semi-circular ratchet portions concentric with the hinge pin; a pair of diametrically opposed slide pawls slidably coupled within the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portions of the second arm member; and a cam element slidably coupled within the first arm member in a lateral direction perpendicular to the slide pawls and disposed between the slide pawls, the cam element being operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction perpendicular to the slide pawls for engaging the slide pawls with the ratchet portions of the second arm member and for disengaging the slide pawls from the ratchet portions of the second arm member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawls in engagement with the ratchet portions of the second arm member.
 6. A reclining mechanism for a vehicle seat, comprising: a first arm member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat; a second arm member for attachment to a frame structure of the other of the back rest or the seat cushion, the second arm member being connected with the first arm member by means of a hinge pin for relative rotation about the hinge pin and having a pair of diametrically opposed semi-circular ratchet portions concentric with the hinge pin; a pair of diametrically opposed slide pawls slidably coupled within the first arm member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portions of the second arm member; and a cam element slidably coupled within the first arm member in a lateral direction perpendicular to the slide pawls and disposed between the slide pawls, the cam element being operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawls with the ratchet portions of the second arm member and for disengaging the slide pawls from the ratchet portions of the second arm member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawls in engagement with the ratchet portions of the second arm member, and wherein the slide pawls each are formed at their outer ends with a semi-circular toothed portion for engagement with each ratchet portion of the second arm member and at their inner ends with a pair of laterally spaced projections to be engaged with opposite flat surfaces of the cam element for maintaining the slide pawls in engagement with the ratchet portions of the second arm member, and wherein the cam element is formed at the opposite flat surfaces thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawls for permitting disengagement of the slide pawls from the ratchet portions of the second arm member.
 7. A reclining mechanism as claimed in claim 6, wherein a cam plate is assembled with the cam element to disengage the slide pawls from the ratchet portions of the second arm member by engagement therewith when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element.
 8. A reclining mechanism as claimed in claim 7, wherein said cam plate is formed with a pair of diametrically opposed cam slots which are engaged with a pair of cam pins provided on the slide pawls to disengage the slide pawls from the ratchet portions of the second arm member when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element.
 9. A reclining mechanism as claimed in claim 6, wherein a movable cam plate is assembled with the hinge pin to be rotated with the hinge pin and rotatably connected with the cam element to cause lateral movement of the cam element when rotated with the hinge pin, and wherein the movable cam plate is formed with a pair of diametrically opposed cam slots which are engaged with a pair of cam pins provided on the slide pawls to disengage the slide pawls from the ratchet portions of the second arm member when the hinge pin is rotated against the load of the torsion spring.
 10. A reclining mechanism as claimed in claim 6, wherein the slide pawls each are formed with a recessed portion between the spaced projections thereof, and wherein the cam element is formed with a pair of radial projections to be engaged with the recessed portions of the slide pawls for disengaging the slide pawls from the ratchet portions of the second arm member when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element.
 11. A reclining mechanism for a vehicle seat, comprising: a first disk member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat; a second disk member for attachment to a frame structure of the other of the back rest or the seat cushion, the second disk member being coupled with the first disk member for relative rotation and united with the first disk member by means of an annular bracket coupled therewith and having an internal semi-circular ratchet portion concentric therewith; a hinge pin assembled with the disk members in such a manner as to permit relative rotation of the disk member; a slide pawl slidably coupled within the first disk member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portion of the second disk member; and a cam element slidably coupled within the first disk member in a lateral direction perpendicular to the slide pawl and operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawl with the ratchet portion of the first disk member and for disengaging the slide pawl from the ratchet portion of the first disk member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawl in engagement with the ratchet portion of the second disk member, and wherein the slide pawl is formed at its outer end with a semi-circular toothed portion to be engaged with the ratchet portion of the second disk member and its inner end with a pair of laterally spaced projections for engagement with a flat end surface of the cam element; and wherein the cam element is formed at the flat end surface thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawl for permitting disengagement of the slide pawl form the ratchet portion of the second disk member.
 12. A reclining mechanism for a vehicle seat, comprising: a first disk member for attachment to a frame structure of a seat cushion or a back rest of the vehicle seat; a second disk member for attachment to a frame structure of the other of the back rest or the seat cushion, the second disk member being coupled with the first disk member for relative rotation and united with the first disk member by means of an annular bracket coupled therewith and having a pair of diametrically opposed internal semi-circular ratchet portions concentric therewith; a hinge pin assembled with the disk members in such a manner as to permit relative rotation of the disk members; a pair of diametrically opposed slide pawls slidably coupled within the first disk member in a radial direction with respect to the hinge pin to be moved toward and away from the ratchet portions of the second disk member; and a cam element slidably coupled within the first disk member in a lateral direction perpendicular to the slide pawls and disposed between the slide pawls, the cam element being operatively connected with the hinge pin to be moved by rotation of the hinge pin in the lateral direction for engaging the slide pawls with the ratchet portions of the second disk member and for disengaging the slide pawls from the ratchet portions of the second disk member, wherein the hinge pin is loaded by a torsion spring assembled thereon to bias the cam element in the lateral direction for maintaining the slide pawls in engagement with the ratchet portions of the second disk member.
 13. A reclining mechanism as claimed in claim 12, wherein the slide pawls each are formed at their outer ends with a semi-circular toothed portion for engagement with each ratchet portion of the second disk member and at their inner ends with a pair of laterally spaced projections to be engaged with opposite flat surfaces of the cam element for maintaining the slide pawls in engagement with the ratchet portions of the second disk member, and wherein the cam element is formed at the opposite flat surfaces thereof with a pair of laterally spaced recesses to be engaged with the spaced projections of the slide pawls for permitting disengagement of the slide pawls from the ratchet portions of the second disk member.
 14. A reclining mechanism as claimed in claim 13, wherein the slide pawls each are formed with a recessed portion between the spaced projections thereof, and wherein the cam element is formed with a pair of radial projections to be engaged with the recessed portions of the slide pawls for disengaging the slide pawls from the ratchet portions of the second disk member when the hinge pin is rotated against the load of the torsion spring to cause lateral movement of the cam element. 